1. Field of the Invention
The present invention relates to a method of manufacturing a fuel cell electrode, and particularly, to a method of manufacturing a fuel cell anode for a Polymer Electrolyte Membrane Fuel Cell (PEMFC).
2. Description of Related Art
The membrane electrode assembly (MEA) structure of a Polymer Electrolyte Membrane Fuel Cell mainly consists of an anode, a cathode and a proton-conducting polymer electrolyte membrane disposed between the anode and the cathode.
In general, multiple membrane electrode assemblies are stacked up against each other to form a polymer electrolyte membrane fuel cell stack.
Catalysts of the anode and the cathode mainly have the form of homogenous or heterogeneous noble metal nanoparticles uniformly distributed on the surface of a conductive porous support. The noble metal nanoparticles bring the oxidation of fuel and the reduction of oxygen at the anode and the cathode, respectively. The porous support is typically a carbon material.
When driving a fuel cell vehicle with the above fuel cell stack mounted therein, a fuel gas passage in the anode may be blocked by produced water or humidification water resulting in flooding of the fuel cell. In addition, when starting the vehicle in a low temperature condition below the freezing point, any water remaining in the anode is frozen to block the gas passage of the anode.
In this case, if the anode lacks a supply of fuel (H2) due to blockage of the gas passage, the electric potential of the anode is increased, and the fuel cell has a minus value in the total voltage. In other words, a reverse voltage (or potential) phenomenon occurs.
When the fuel cell operates under a reverse voltage condition, the carbon serving as the support gradually or rapidly oxidizes and the electrode structure collapses. This results in degradation in the performance of the fuel cell.
Among various approaches suggested to reduce the constraint associated with the carbon oxidation of the anode, one involves use of a catalyst capable of electrolyzing water added to the fuel cell anode such that electrons are supplied not from the carbon but from the water when the reverse potential occurs. To this end, an oxide catalyst capable of electrolyzing water, for example, ruthenium oxide (RuOx), iridium Oxide (IrOx), a rubidium compound, an iridium compound, iridium metal and the like, is synthesized, and then the oxide catalyst is mixed with a general anode catalyst, thereby forming the electrode.
However, the water electrolysis catalyst operates through a solvent-based reduction/oxidation, so the process is complicated and manufacture of the catalyst is a lengthy process. In addition, the conventional manufacturing method for forming such a catalyst causes a difficulty in implementing a desired MEA electrode structure. This is due to the water splitting catalyst which, due to its own physical/chemical properties such as affinity and suitability for the solvent, exerts an influence on the porous structure of the electrode and the dispersion of ionomer.